Relatively inexpensive honing machines are currently used in small engine reconditioning shops for finishing rebored workpieces, such as engine blocks. A common type of honing machine used for such purposes is often referred to at a "beam stroker." A machine of this type is disclosed in U.S. Pat. No 4,189,871. In such machines, an expandable honing tool is suspended from a pivoted arm or "beam" which contains mechanism for rotating and expanding the tool. The beam is swung up and down or "stroked" to vertically reciprocate the rotating honing tool within the workpiece, thereby honing the inner surface of the rebored workpiece.
One problem often encountered in honing operations is lower bore taper. Ideally, the honing machine would be adjusted such that the honing tool extends out the lower end of the bore approximately 3/4 inch at the bottom of the stroke. In many engine blocks, however, such extension is impossible because of a web member on the engine block which blocks passage of the honing tool. Consequently, the lower regions of a cylindrical bore will not be adequately honed by the normal stroking process and will require additional honing to remove excess material for a proper finish. Existing honing machines enable the machine operator to interrupt stroking of the honing tool at the bottom of the stroke so that the honing tool will dwell in the bottom of the bore, thereby removing the excess material which creates the lower bore taper.
Allowing the honing tool to dwell at the bottom of its stroke will remove lower bore tapers more effectively than normal stroking of the tool within the entire bore, but several disadvantages remain with existing dwelling procedures. First, removing excess material while the tool is held vertically stationary is a relatively slow procedure. Additionally, when the honing tool is rotated at a fixed elevation within the bore, vibration and chatter will result, tending to produce a bad finish. Also, when the tool is not stroking, the stones of the tool will tend to "load up" as the material removed during honing glazes over the stones, reducing their efficiency.